If log file cannot be written, show error dialog and exit. On Mac, explain how to enable Document Folder permission and open System Settings before exit.

adapters/standalone.cpp

@@ -134,7 +134,17 @@ int main(int argc, char* argv[]) {
 	if (!settings::devMode) {
 		logger::logPath = asset::user("log.txt");
 	}
-	logger::init();
+	if (!logger::init()) {
+		std::string msg = "Cannot access Rack's user folder " + asset::userDir;
+#if defined ARCH_MAC
+		// The user likely clicked "Don't Allow" on the Documents Folder permissions dialog, so tell them how to allow it.
+		msg += "\n\nMake sure Rack has permission by opening Apple's System Settings and enabling Privacy & Security > Files and Folders > " + APP_NAME + " " + APP_VERSION_MAJOR + " " + APP_EDITION_NAME + " > Documents Folder.";
+		// Launch Apple's Privacy & Security settings
+		std::system("open x-apple.systempreferences:com.apple.preference.security");
+#endif
+		osdialog_message(OSDIALOG_ERROR, OSDIALOG_OK, msg.c_str());
+		exit(1);
+	}
 	random::init();
 
 	// Test code

include/logger.hpp

@@ -31,7 +31,8 @@ enum Level {
 	FATAL_LEVEL
 };
 
-PRIVATE void init();
+/** Returns whether logger was successfully initialized. */
+PRIVATE bool init();
 PRIVATE void destroy();
 /** Do not use this function directly. Use the macros above.
 Thread-safe, meaning messages cannot overlap each other in the log.

src/logger.cpp

@@ -46,8 +46,10 @@ static bool isTruncated() {
 }
 
 
-void init() {
-	assert(!outputFile);
+bool init() {
+	if (outputFile)
+		return true;
+
 	std::lock_guard<std::mutex> lock(mutex);
 	truncated = false;
 
@@ -61,13 +63,11 @@ void init() {
 		outputFile = std::fopen(logPath.c_str(), "w");
 		if (!outputFile) {
 			std::fprintf(stderr, "Could not open log at %s\n", logPath.c_str());
+			return false;
 		}
 	}
 
-	// Redirect stdout and stderr to the file
-	// Actually, disable this because we don't want to steal stdout/stderr from the DAW in Rack for DAWs.
-	// dup2(fileno(outputFile), fileno(stdout));
-	// dup2(fileno(outputFile), fileno(stderr));
+	return true;
 }
 
 void destroy() {